I installed this cluster almost 2 year ago and it has always worked fine but some day ago I realized that I have the shared disks mounted also on the stand-by machine!!It’s really strange…I was also able to write from the stand-by server on the shared partitions.

I did an umount of both partitions to re-establish the normal condition, but I’m little bit worried, it isn’t normal this behaviour…

Re: ServiceGuuard and shared disks

Did you implement the exclusive activation feature? What you have seen can happen if you did not implement that and someone manually mounted the file systems. It could have also happened if you did not set up LVM to prevent automatic VG activation.

Re: ServiceGuuard and shared disks

Check the /etc/fstab in both of your cluster nodes. Normally, any ServiceGuard package disks should not be mentioned in /etc/fstab at all... or if they are, they definitely should have the "noauto" mount option.

If some (non-ServiceGuard) "user-friendly" GUI tool was used to prepare the package LVs, it may have automatically added the LVs to /etc/fstab, which would have caused the stand-by system to mount them automatically when it was booted.

In HP-UX, the LVM has a built-in feature that identifies the volume groups belonging to ServiceGuard packages: the HP-UX kernel will refuse to activate the volume groups unless the cluster daemons are active and can positively confirm the VG is not activated elsewhere.

In Linux, there is no such kernel-level mechanism. Originally there was no mechanism in Linux SG that could prevent the activation of the volume groups. The exclusive activation feature was implemented in version 11.16.xx, and works by using the "LVM tags" feature of the 2.6 kernel series. Of course, as it isn't a kernel-level feature, it's not too tough to override it if someone specifically chooses to do so.